# Pelteir\ Thermoelectric Cell Help

Discussion in 'General Electronics Discussion' started by Redshirt214, Dec 31, 2012.

1. ### Redshirt214

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Dec 31, 2012
Currently, I am working on a school project, where I am attempting to generate power using Pelteir Cells. So far, I've succeeded in generating exactly one volt! I'm looking into buying more, newer Pelteir cells ( the ones I'm using were salvaged by my dad, back in the day!), but I have a question. The manufacturer lists how much voltage you can apply to the cell safely. Is this equal to the voltage that you can get out of the cell? Or is it lower\higher than that? Does anybody know?

2. ### Raven Luni

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8
Oct 15, 2011
Quick answer: Anything you can generate from a peltier cell will be relatively tiny compared to the amount of power you have to put in to achieve normal operation (cooling). This is because peltier cells are very inefficient.

Longer answer: If you want to see how much power is generated from a cell, you need to measure in watts, not volts (watts = amps X volts). You also need to plot against the other variables in the system, in this case temperature at both the hot and cold sides. If you take the total energy (in joules) for a given time period, you can compare the figures for electrical and heat energy to give you a rough efficiency figure. Your physics teacher should have told you all this anyway

3. ### Redshirt214

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Dec 31, 2012
Thank you for your response, I suspected so as much, based off of what I have read. I appreciate your help, as the project I'm working on more or less requires me to do all of my own research, and I've so far been unsuccessful at locating an expert on Pelteir cells. So what should I do then? Buy the most powerful cell I can, and hope for the best, or buy a lot of smaller cells and build an array? Also, do Pelteir cells efficiency decrease with age?

4. ### Harald KappModeratorModerator

10,764
2,424
Nov 17, 2011
Here is some general information on Peltiers, also here. A Peltier (btw: note the spelling) will deliver only a limited voltage which depends on the construction of the element. A commercial Peltier is usually made from several small Peltier cells. each cell can deliver only a limited voltage and amperage. In order to increase the power of a Peltier element, many of these cells are connected either in series or in parallel, or both.
If the cells are in series, the voltage at the terminals increases, but the current stays small.
If the cells are in parallel, the voltage stays small but the current increases.
If they are connected in series and parallel, both voltage and current increase, but to a lesser extend.
And power , as Raven already stated, is V*I.

It were best if you had access to the Peltier element's datasheet. If not, measure the open circuit voltage and the short circuit current to get at least a feeling for the corner characteristics of the element.

If you're going to buy Peltier elements, you need to specify your requirements, but you will still be hard pressed to find data for reverse operation of a Peltier element (i.e. generate power from thermal difference). In a first approximation, for any given temperature difference you will not be able to generate as much electrical power as you need to generate that temperature difference from electrical energy (the latter being routinely stated in the datasheet).